Fused aminopiperidines as dipeptidyl peptidase-4 inhibitors for the treatment or prevention of diabetes

1. A compound of structural formula I:

or a pharmaceutically acceptable salt thereof; wherein

each n is independently 0, 1, 2 or 3;

Ar is phenyl unsubstituted or substituted with one to five R 2 substituents;

each R 2 is independently selected from the group consisting of

halogen,

cyano,

hydroxy,

C 1-6 alkyl, unsubstituted or substituted with one to five halogens, and

C 1-6 alkoxy, unsubstituted or substituted with one to five halogens;

W, X, Y, and Z are selected from the following:

wherein W is N; and X, Y, and Z are CR 1 ;

wherein Z is N; and W, X, and Y are CR 1 ;

wherein W and Y are N; and X and Z are CR 1 ;

wherein X and Z are N; and W and Y are CR 1 ;

wherein W and X are N; and Y and Z are CR 1 ;

wherein X and Y are N; and W and Z are CR 1 ;

wherein Y and Z are N; and W and X are CR 1 ;

wherein W and Z are N; and X and Y are CR 1 ;

each R 1 is independently selected from the group consisting of

hydrogen,

hydroxy,

halogen,

cyano,

nitro,

C 1-10 alkoxy, wherein alkoxy is unsubstituted or substituted with one to five substituents independently selected from halogen or hydroxy,

C 1-10 alkyl, wherein alkyl is unsubstituted or substituted with one to five substituents independently selected from halogen or hydroxy,

(CH 2 ) n -aryl, wherein aryl is unsubstituted or substituted with one to five substituents independently selected hydroxy, halogen, cyano, CO 2 H, C 1-6 alkyloxycarbonyl, C 1-6 alkyl, and C 1-6 alkoxy, wherein alkyl and alkoxy are unsubstituted or substituted with one to five halogens,

(CH 2 ) n -heteroaryl, wherein heteroaryl is unsubstituted or substituted with one to three substituents independently selected from hydroxy, halogen, cyano, CO 2 H, C 1-6 alkyloxycarbonyl, C 1-6 alkyl, and C 1-6 alkoxy, wherein alkyl and alkoxy are unsubstituted or substituted with one to five halogens,

(CH 2 ) n -heterocyclyl, wherein heterocyclyl is unsubstituted or substituted with one to three substituents independently selected from oxo, hydroxy, halogen, cyano, CO 2 H, C 1-6 alkyloxycarbonyl, C 1-6 alkyl, and C 1-6 alkoxy, wherein alkyl and alkoxy are unsubstituted or substituted with one to five halogens,

(CH 2 ) n —C 3-6 cycloalkyl, wherein cycloalkyl is unsubstituted or substituted with one to three substituents independently selected from halogen, hydroxy, cyano, CO 2 H, C 1-6 alkyloxycarbonyl, C 1-6 alkyl, and C 1-6 alkoxy, wherein alkyl and alkoxy are unsubstituted or substituted with one to five halogens,

(CH 2 ) n —COOH,

(CH 2 ) n —COOC 1-6 alkyl,

(CH 2 ) n —NR 3 R 4 ,

(CH 2 ) n —CONR 3 R 4 ,

(CH 2 ) n —OCONR 3 R 4 ,

(CH 2 ) n —SO 2 NR 3 R 4 ,

(CH 2 ) n —SO 2 R 5 ,

(CH 2 ) n —SOR 5 ,

(CH 2 ) n —SR 6 ,

(CH 2 ) n —NR 6 SO 2 R 5 ,

(CH 2 ) n —NR 6 CONR 3 R 4 ,

(CH 2 ) n —NR 6 COR 6 , and

(CH 2 ) n —NR 6 CO 2 R 5 ;

wherein any individual methylene (CH 2 ) carbon atom in (CH 2 ) n is unsubstituted or substituted with one to two groups independently selected from halogen, hydroxy, C 1-4 alkyl, and C 1-4 alkoxy, wherein alkyl and alkoxy are unsubstituted or substituted with one to five halogens;

R 3 and R 4 are each independently selected from the group consisting of

hydrogen,

(CH 2 ) n -phenyl,

(CH 2 ) n —C 3-6 cycloalkyl, and

C 1-6 alkyl,

wherein alkyl is unsubstituted or substituted with one to five substituents independently selected from halogen and hydroxy and wherein phenyl and cycloalkyl are unsubstituted or substituted with one to five substituents independently selected from halogen, hydroxy, C 1-6 alkyl, and C 1-6 alkoxy, wherein alkyl and alkoxy are unsubstituted or substituted with one to five halogens; or R 3 and R 4 together with the nitrogen atom to which they are attached form a heterocyclic ring selected from azetidine, pyrrolidine, piperidine, piperazine, and morpholine wherein said heterocyclic ring is unsubstituted or substituted with one to three substituents independently selected from halogen, hydroxy, C 1-6 alkyl, and C 1-6 alkoxy, wherein alkyl and alkoxy are unsubstituted or substituted with one to five halogens;

each R 5 is independently C 1-6 alkyl, wherein alkyl is unsubstituted or substituted with one to five substituents independently selected from halogen and hydroxy; and

R 6 is hydrogen or R 5 .

2. The compound of claim 1 wherein each R 2 is independently selected from the group consisting of fluorine, chlorine, methyl, and trifluoromethyl.

3. The compound of claim 1 of structural formula Ia or Ib having the indicated stereochemical configuration at the two stereogenic carbon atoms marked with an *:

4. The compound of claim 3 of structural formula Ia having the indicated absolute stereochemical configuration at the two stereogenic carbon atoms marked with an *:

5. The compound of claim 4 which is selected from

the group consisting of:

or a pharmaceutically acceptable salt thereof.

6. A pharmaceutical composition which comprises a compound of claim 1 and a pharmaceutically acceptable carrier.

7. The pharmaceutical composition of claim 6 additionally comprising metformin.

8. A method for treating non-insulin dependent (Type 2) diabetes in a mammal in need thereof which comprises the administration to the mammal of a therapeutically effective amount of a compound of claim 1 .